我的问题非常接近这个问题:FBO and Render to renderbuffer。
我目前正在尝试在像tutorial这样的renderbuffer上渲染一个简单的三角形。我的程序是Igor Pro的插件，该插件使用OpenGL执行屏幕外渲染。
不幸的是，当我尝试读取像素值时，我得到的只有零。
我已经知道initBuffers函数有效，问题出在display函数中。
1)我的代码有什么问题？
2)我想在不使用立即模式的情况下呈现顶点数据列表。我以前已经使用VBO完成了实现。我可以重用该代码吗？
我的代码如下:
/*
RenderTriangle.cpp
*/
#include "VC10\triangulation.h"
#include "XOPStandardHeaders.h" // Include ANSI headers, Mac headers, IgorXOP.h, XOP.h and XOPSupport.h
#include <vector>
// Prototypes
HOST_IMPORT int main(IORecHandle ioRecHandle);
// Global Variables
const int windowSize = 512;
int size,el_size;
float* waveX=NULL;
float* waveY=NULL;
float* waveZ=NULL;
GLuint framebuffer, renderbuffer;
// Custom error codes
#define OLD_IGOR 1 + FIRST_XOP_ERR
#define NON_EXISTENT_WAVE 2 + FIRST_XOP_ERR
#define REQUIRES_SP_OR_DP_WAVE 3 + FIRST_XOP_ERR
#pragma pack(2) // All structures passed to Igor are two-byte aligned.
typedef struct WaveParams {
waveHndl waveZ;
waveHndl waveY;
waveHndl waveX;
double result;
} WaveParams, *WaveParamsPtr;
#pragma pack() // Restore default structure alignment
// Prototypes of the OpenGL callbacks
void initBuffers(void);
void display(void);
void readPixels(void);
void initBuffers(void){
GLenum status;
//Generate the fbo where we will bind a render buffer object
glGenFramebuffers(1,&framebuffer);
glBindFramebuffer(GL_DRAW_FRAMEBUFFER,framebuffer);
//Generate render buffer object
glGenRenderbuffers(1,&renderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER,renderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER,GL_RGBA8, windowSize, windowSize);
glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, renderbuffer);
status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE)
XOPNotice("Error Framebuffer Complete");
else
XOPNotice("Framebuffer Complete");
}
void display(void){//display a simple triangle
glViewport(0,0,windowSize,windowSize);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glClearColor(1.0f, 0.0f, 0.0f,0.5f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glBegin(GL_TRIANGLES);// Drawing Using Triangles
glColor3f(1.0f, 0.0f, 0.0f);glVertex3f( 0.0f, 1.0f, 0.0f);// Top
glColor3f(1.0f, 0.0f, 0.0f);glVertex3f(-1.0f,-1.0f, 0.0f);// Bottom Left
glColor3f(1.0f, 0.0f, 0.0f);glVertex3f( 1.0f,-1.0f, 0.0f);// Bottom Right
glEnd();// Finished Drawing The Triangle
glFlush();
}
// Idle callback function for OpenGL API
void readPixels(void){
//glBindFramebuffer(GL_FRAMEBUFFER, 0);
float* pixels = (float*)malloc(windowSize*windowSize*sizeof(float));
glReadBuffer(GL_COLOR_ATTACHMENT0);
glReadPixels(0, 0, windowSize, windowSize, GL_DEPTH_COMPONENT, GL_FLOAT, pixels);
waveHndl waveH;
char waveName[MAX_OBJ_NAME+1];
DataFolderHandle dfH;
CountInt dimensionSizes[MAX_DIMENSIONS+1];
float* wp;
IndexInt p;
double offset, delta;
int err;
strcpy(waveName, "wave1");
dfH = NULL; // Put wave in the current data folder
MemClear(dimensionSizes, sizeof(dimensionSizes));
dimensionSizes[ROWS] = windowSize; // Make 1D wave with 100 points
dimensionSizes[COLUMNS] = windowSize;
if (MDMakeWave(&waveH, waveName, dfH, dimensionSizes, NT_FP32, 1))
XOPNotice("Can't create wave when reading pixel values");
wp = (float*)WaveData(waveH); // Get a pointer to the wave data
for(p = 0; p < windowSize*windowSize; p++)
*wp++ = pixels[p]; // Store point number in wave
}
void deleteBuffers(){
glDeleteFramebuffers(1,&framebuffer);
glDeleteRenderbuffers(1,&renderbuffer);
}
// Main function for the XOP
extern "C" int
RenderTriangle(WaveParamsPtr p)
{
//Pointers to the input waves
waveX=(float*)WaveData(p->waveX);
waveY=(float*)WaveData(p->waveY);
waveZ=(float*)WaveData(p->waveZ);
//Creates the window
char *myargv [1];
int myargc=1, windowHandle;
myargv [0]=strdup ("RenderTriangle");
glutInit(&myargc,myargv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_DEPTH | GLUT_RGB);
glutInitWindowSize(windowSize,windowSize);
windowHandle = glutCreateWindow("OpenGL");
//Init glew library
glewInit();
//Creates the fbo and render buffer object
initBuffers();
display();
readPixels();
//Deletes the fbo and render buffer object
deleteBuffers();
p->result = 1;
return 0;
}
static XOPIORecResult
RegisterFunction()
{
int funcIndex;
funcIndex = (int)GetXOPItem(0); // Which function invoked ?
switch (funcIndex) {
case 0: // y = RenderTriangle(w,x) (curve fitting function).
return (XOPIORecResult)RenderTriangle; // This function is called using the direct method.
break;
}
return 0;
}
/* XOPEntry()
This is the entry point from the host application to the XOP for all
messages after the INIT message.
*/
extern "C" void
XOPEntry(void)
{
XOPIORecResult result = 0;
switch (GetXOPMessage()) {
case FUNCADDRS:
result = RegisterFunction(); // This tells Igor the address of our function.
break;
}
SetXOPResult(result);
}
/* main(ioRecHandle)
This is the initial entry point at which the host application calls XOP.
The message sent by the host must be INIT.
main() does any necessary initialization and then sets the XOPEntry field of the
ioRecHandle to the address to be called for future messages.
*/
HOST_IMPORT int
main(IORecHandle ioRecHandle)
{
XOPInit(ioRecHandle); // Do standard XOP initialization.
SetXOPEntry(XOPEntry); // Set entry point for future calls.
if (igorVersion < 600) {
SetXOPResult(OLD_IGOR);
return EXIT_FAILURE;
}
SetXOPResult(0);
return EXIT_SUCCESS;
}
最佳答案
您需要一个正常工作的OpenGL上下文，其余的函数才能正常工作，而不创建一个上下文!您使用GLUT作为框架，但是GLUT仅在调用glutCreateWindow时创建渲染上下文。在此之前，您根本没有 Activity 的RC，其余的将无法使用。
也许Igor自己在某个时候创建了一个OpenGL上下文，而您正在将其扔进去。
而不是使用GLUT，您应该使用系统级API来
关于c++ - 用FBO绘制到renderbuffer，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/15800329/